Migrate to LittleFS under ESP8266

Make ESP8266 use LittleFS instead of deprecated SPIFFS
Make framework use the correct filesystem automatically and handle the call the FS.begin()
Change default MQTT keepalive to 60 seconds
Fix lodash security issue

factory_settings.ini

@@ -38,7 +38,7 @@ build_flags =
     -D FACTORY_MQTT_PASSWORD=\"\"
     ; if unspecified the devices hardware ID will be used
     ;-D FACTORY_MQTT_CLIENT_ID=\"esp-react\"
-    -D FACTORY_MQTT_KEEP_ALIVE=16
+    -D FACTORY_MQTT_KEEP_ALIVE=60
     -D FACTORY_MQTT_CLEAN_SESSION=true
     -D FACTORY_MQTT_MAX_TOPIC_LENGTH=128